The present invention relates to a prosthetic sleeve, and more exactly a sleeve member intended to be adapted to and attached to a body portion like an amputation stump.
In connection with amputation of an extremity e.g. a leg, a so called amputation stump is normally kept, that is to say some portion of the amputated extremity is left to serve as an attachment for a suitable prosthesis.
A suitably adapted sleeve member is slipped over the remaining stump and constitutes in this way a fastening for the real prosthetic device, which for example may be a foot or a lower leg with foot in case the stump is situated below the knee of a leg. Similarly the prosthesis may be an entire prosthetic leg, whereby a remaining portion of the thigh bone is fitted into a corresponding prosthetic sleeve. In a corresponding way a lower arm or an upper arm prosthesis is attached.
Such a sleeve member consists of a conical shape, one end of which is open and the other is completely closed and having a somewhat rounded off shape. Additionally the sleeve member is plastic to be adapted to an amputation stump.
In conventional provisions of prosthetic devices for, e.g. an amputated extremity, it is consequently confining what is left of the extremity in a specially adapted sleeve attached to the prosthesis, transferring forces between the prosthesis and the remaining portion of the extremity.
A specially adapted sleeve is made by producing an exact copy of what is left of this extremity. Today there are mainly two methods utilized to do this, either a laser scanner is used which is imaging the body portion to be copied, then the values read by the scanner are transferred to a milling cutter, which mills a copy of the body portion, or a negative plaster cast is made by means of plaster bandage, whereafter the negative plaster cast is filled to create an exact positive copy of the body portion. Then by means of the positive copy a normally rigid prosthetic sleeve is molded, which may be placed onto the amputation stump. The disadvantage with such copies is that they are exact only at the time of the plaster casting. The reason for this is that the human body is continuously changing and especially then the portion left of an amputated extremity, the atrophy being large (in time it decreases in volume).
The problem of the rigid sleeve is that it does not follow the changes in volume and what is left of the extremity is soft and sensitive while the sleeve member is hard, which easily results in being chafed if there is not a softer sleeve inside the rigid sleeve. Therefore today some different kinds of soft sleeves are made to be used with such rigid outer sleeves.
Today a commonly found soft sleeve is an American product which is normally referred to as the Alpha sleeve. The Alpha sleeve is made from a thick thermoplastic elastic material, which was necessary to reinforce by an outer layer of fabric. The advantage of the Alpha sleeve is that it is possible to adapt it to a certain extent to the stump of the patient, which means that many problems are avoided. The drawback is that it must be reinforced by the outer layer of fabric, which implies that the stump cannot be seen through the sleeve. If the stump cannot be seen through the sleeve it is not possible to decide if the sleeve is correctly adapted. If a specifically adapted sleeve is incorrectly placed the pressure stress at dangerous spots may be increased. Additionally it is not seen whether a decreased stress is to be arranged over some prominence. Furthermore it is not simple to attach a stress-relief to the Alpha sleeve due to the layer of fabric. The layer of fabric also limits the adaptability, the fabric may only be stretched to a certain limit, and a small uneven stress over the prominences will be introduced.
Today another frequently found inner sleeve is one made of silicone and disclosed in the Swedish Patent document SE 454 943. The problem of this sleeve is that it is not able to be particularly adapted to the amputation stump. The sleeve instead is so elastic that it can encircle the amputation stump, but as no amputation stump in reality is shaped conically, there will be higher pressure and stress onto the following portions of the stump:
In areas where the diameter of the stump is larger than the silicone sleeve, which means that the surface pressure will be higher to the stump in this area compared to other areas.
In areas, where the stump has a small radius, e.g. a prominence due to underlying bone, which means that the surface pressure over the prominence itself locally increases when the elastic sleeve is tightened over the prominence. Also see example of FIG. 4, which symbolizes an elastic sleeve rolled onto a stump of a lower leg amputee, illustrating how the distal tibia point creates a bone prominence downmost to the left in FIG. 4, which is a common view.
Not only the pressure at these exposed portions will increase, but with this stretching of the sleeve in these more sensitive areas a larger loss of entropy takes place in the sleeve at these areas, in other words the molecule chains are stretched, which in turn decreases their mobility, the soft sleeve becomes harder in the sensitive areas.
Elastic materials harden when they are stretched, but in the case above an uneven hardening will be achieved where the harder portions are placed at the portions being most stressed, which results in discomfort and the user being chafed.
Most of the users of prosthetic devices are lower leg amputated and elderly and therefore do sit quite a lot when they use their prosthetic device. The problem of the frequently seen soft prosthetic sleeves of today is that they fold at the back of the knee when the knee is bent, which results in discomfort and being chafed and, in the worst case, that the flow of blood is obstructed and that a so called stasis condition arises. Note in FIG. 4 how the sleeve is folded at its upper right portion.
Therefore there is a need of a prosthetic sleeve for which the disadvantages mentioned above will be avoided to thereby for an amputated patient create an aiding prosthetic means which presents a good flexibility but at the same time provides a good stability.
The disadvantages described above are solved by means of a prosthetic sleeve according to the present invention. The new prosthetic sleeve according to the invention constitutes a sleeve member having a conical shape where one end is open and the other completely closed with a somewhat rounded shape. The sleeve member which is made of a thermoplastic elastomer (TPE material) may be formed with heat and is transparent, soft and kind to the skin, which results in that it better can be adapted to any amputation stump.